The Occurrence of Peroxiredoxins and Changes in Redox State in Acer platanoides and Acer pseudoplatanus During Seed Development

Journal of Plant Growth Regulation - Norway maple (Acer platanoides L.) and sycamore (A. pseudoplatanus L.) are genetically closely related species that produce desiccation-tolerant (orthodox) and...     

Low amounts of herbivory by root-knot nematodes affect microbial community dynamics and carbon allocation in the rhizosphere

Increased carbon translocation to the rhizosphere via 'leakage' induced by low amounts of plant parasitic nematodes can foster microorganisms. The effects of the root-knot nematode Meloidogyne incognita on microbial biomass (C(mic)) and community structure (phospholipid fatty acids) in the rhizosphere of barley were studied. Inoculation densities of 2000, 4000, and 8000 nematodes were well below the threshold level for plant damage. A (13)CO(2) pulse-labelling was performed to assess the distribution of assimilated (13)C in the rhizosphere. Infection with M. incognita increased the carbon concentration in shoots, and enhanced root biomass slightly. The presence of nematodes did not affect microbial biomass, but significantly changed the allocation of the recent photosynthate. Less plant carbon was sequestered by microorganisms with increasing nematode abundance. Microbial community structure was distinctly altered in the early stages of the plant-nematode interactions. Both, bacteria and fungi, showed a positive response with 2000, and a negative one with 4000 and 8000 M. incognita added. The results suggest that low-level root herbivory still imposes a considerable carbon demand, and that proliferation of microorganisms due to increased rhizodeposition may be short-termed. The carbon flow to rhizosphere microbial communities is likely dependent on the specific nematode-plant association and the developmental stage of the nematode in the host.     

Functional and Biochemical Characterization of Cucumber Genes Encoding Two Copper ATPases CsHMA5.1 and CsHMA5.2

Plant copper P_1B-type ATPases appear to be crucial for maintaining copper homeostasis within plant cells, but until now they have been studied mostly in model plant systems. Here, we present the molecular and biochemical characterization of two cucumber copper ATPases, CsHMA5.1 and CsHMA5.2, indicating a different function for HMA5-like proteins in different plants. When expressed in yeast, CsHMA5.1 and CsHMA5.2 localize to the vacuolar membrane and are activated by monovalent copper or silver ions and cysteine, showing different affinities to Cu⁺ (K_m ∼1 or 0.5 μm, respectively) and similar affinity to Ag⁺ (K_m ∼2.5 μm). Both proteins restore the growth of yeast mutants sensitive to copper excess and silver through intracellular copper sequestration, indicating that they contribute to copper and silver detoxification. Immunoblotting with specific antibodies revealed the presence of CsHMA5.1 and CsHMA5.2 in the tonoplast of cucumber cells. Interestingly, the root-specific CsHMA5.1 was not affected by copper stress, whereas the widely expressed CsHMA5.2 was up-regulated or down-regulated in roots upon copper excess or deficiency, respectively. The copper-induced increase in tonoplast CsHMA5.2 is consistent with the increased activity of ATP-dependent copper transport into tonoplast vesicles isolated from roots of plants grown under copper excess. These data identify CsHMA5.1 and CsHMA5.2 as high affinity Cu⁺ transporters and suggest that CsHMA5.2 is responsible for the increased sequestration of copper in vacuoles of cucumber root cells under copper excess.     

Site‐specific dynamics in remnant populations of Northern Wheatears Oenanthe oenanthe in the Netherlands

Dynamics of populations may be synchronized at large spatial scales, indicating driving forces acting beyond local scales, but may also vary locally as a result of site‐specific conditions. Conservation measures for fragmented and declining populations may need to address such local effects to avoid local extinction before measures at large spatial scales become effective. To assess differences in local population dynamics, we aimed to determine the demographic drivers controlling population trends in three remaining populations of the Northern Wheatear Oenanthe oenanthe in the Netherlands, as a basis for conservation actions. An integrated population model (IPM) was fitted to field data collected in each site in 2007–2011 to estimate fecundity, survival and immigration. Sites were 40–120 km apart, yet first‐year recruits were observed to move between some of the sites, albeit rarely. All three populations were equally sensitive to changes in fecundity and first‐year survival. One population was less sensitive to adult survival but more sensitive to immigration. A life table response experiment suggested that differences in immigration were important determinants of differences in population growth between sites. Given the importance of immigration for local dynamics along with high philopatry, resulting in low exchange between sites, creating a metapopulation structure by improving connectivity and the protection of local populations are important for the conservation of these populations. Site‐specific conservation actions will therefore be efficient and, for the short term, we propose different site‐specific conservation actions.     

Mapping of a N-terminal α-helix domain required for human PINK1 stabilization,Serine228 autophosphorylation and activation in cells

Autosomal recessive mutations in the PINK1 gene are causal for Parkinson''s disease (PD). PINK1 encodes a mitochondrial localized protein kinase that is a master-regulator of mitochondrial quality control pathways. Structural studies to date have elaborated the mechanism of how mutations located within the kinase domain disrupt PINK1 function; however, the molecular mechanism of PINK1 mutations located upstream and downstream of the kinase domain is unknown. We have employed mutagenesis studies to define the minimal region of human PINK1 required for optimal ubiquitin phosphorylation, beginning at residue Ile111. Inspection of the AlphaFold human PINK1 structure model predicts a conserved N-terminal α-helical extension (NTE) domain forming an intramolecular interaction with the C-terminal extension (CTE), which we corroborate using hydrogen/deuterium exchange mass spectrometry of recombinant insect PINK1 protein. Cell-based analysis of human PINK1 reveals that PD-associated mutations (e.g. Q126P), located within the NTE : CTE interface, markedly inhibit stabilization of PINK1; autophosphorylation at Serine228 (Ser228) and Ubiquitin Serine65 (Ser65) phosphorylation. Furthermore, we provide evidence that NTE and CTE domain mutants disrupt PINK1 stabilization at the mitochondrial Translocase of outer membrane complex. The clinical relevance of our findings is supported by the demonstration of defective stabilization and activation of endogenous PINK1 in human fibroblasts of a patient with early-onset PD due to homozygous PINK1 Q126P mutations. Overall, we define a functional role of the NTE : CTE interface towards PINK1 stabilization and activation and show that loss of NTE : CTE interactions is a major mechanism of PINK1-associated mutations linked to PD.     

Diversity and Drug Resistance of Filamentous Fungi Isolated from the Fresh Raspberries

Fungi are one of the most widely distributed microorganisms in the environment, including food such as fruits, vegetables and other crops, posing a potential threat to food safety and human health. The aim of this study was to determine the diversity, intensity and drug resistance of potentially pathogenic filamentous fungi isolated from the fresh raspberries (Rubus idaeus L.). A total of 50 strains belonging to genera Fusarium, Cladosporium, Alternaria, Penicillium, Mucor, Rhizopus, Aspergillus and Acremonium were tested for drug resistance against 11 antifungals by disc diffusion and gradient strips methods. The average mycological contamination in the examined samples of raspberries amounted to 4.34 log CFU/g. The Cladosporium was isolated from all tested samples, followed by Alternaria and Fusarium with a frequency of 61% and 34%, respectively. The highest level of drug resistance was observed for Acremonium genera and Fusarium strains recorded a wide variation in drug resistance as revealed by susceptibility with amphotericin B and voriconzole with MICs ranged from 0.5–4 µg/ml and posaconazole with MICs ranging from 3–8 µg/ml. All fungal strains showed 100% resistance to caspofungin, fluconazole and flucytosine with both the methods, and 100% resistance to micafungin and anidulafungin in the gradient strip method.     

Molecular and cellular dynamics of early embryonic cell divisions in Volvox carteri

Cell division is fundamental to all organisms and the green alga used here exhibits both key animal and plant functions. Specifically, we analyzed the molecular and cellular dynamics of early embryonic divisions of the multicellular green alga Volvox carteri (Chlamydomonadales). Relevant proteins related to mitosis and cytokinesis were identified in silico, the corresponding genes were cloned, fused to yfp, and stably expressed in Volvox, and the tagged proteins were studied by live-cell imaging. We reveal rearrangements of the microtubule cytoskeleton during centrosome separation, spindle formation, establishment of the phycoplast, and generation of previously unknown structures. The centrosomes participate in initiation of spindle formation and determination of spindle orientation. Although the nuclear envelope does not break down during early mitosis, intermixing of cytoplasm and nucleoplasm results in loss of nuclear identity. Finally, we present a model for mitosis in Volvox. Our study reveals enormous dynamics, clarifies spatio-temporal relationships of subcellular structures, and provides insight into the evolution of cell division.

Analysis of cell divisions of the microalga Volvox reveals enormous dynamics of cytoskeletal and membranous structures with coordination of intranuclear spindle formation by cytosolic centrosomes.

IN A NUTSHELLBackground: Mitosis, a type of cell division, is fundamental to all eukaryotic life and must be carried out very accurately. Even though the process of mitosis itself is highly conserved among eukaryotes, there are significant differences between animals, fungi, plants, and algae. From an evolutionary point of view, the green alga Volvox carteri used here possesses both key animal and plant functions and it exhibits important features of the last common eukaryotic ancestor that have been lost in other lineages. Prior to our work, a comprehensive in vivo analysis of the entire process of cell division in green algae was lacking.Question: How exactly does cell division work in green algae? How do the cytosolic centrosomes deal with the persistent nuclear envelope in this process? What is the relationship between different microtubular structures?Findings: Our study reveals enormous dynamics during mitosis, clarifies spatio-temporal relationships of subcellular structures, and provides insights into evolution of cell division. Although the nuclear envelope does not break down during early mitosis of Volvox, it becomes permeable and the nucleus temporarily loses its identity. Two microtubule-organizing centers, the centrosomes, located immediately outside the nuclear envelope participate in initiation of the mitotic spindle formation inside the nuclear envelope. This process also defines the orientation of the mitotic spindle. In cytokinesis, an algae-specific microtubule structure, the phycoplast, replaces the spindle. The microtubules of the phycoplast may play a direct role in promoting the cell membrane invagination of the cleavage furrow.Next steps: How are the massive rearrangements of subcellular structures regulated? What happens at the nuclear pores when the nuclear envelope becomes permeable at the onset of mitosis? What determines in later embryogenesis which cells then divide asymmetrically rather than symmetrically?